Add SAMx7x timer support

[chris-durand]

• Add support for SAMx7x devices in SAMG55 Timer / Counter driver
• Add example
• Example tested with hardware

[salkinium]

Very nice!

[chris-durand]

These inconsistent SAM headers are sometimes quite disappointing. Variant "A" devices, of course, are missing the register defines for TC_CMR in waveform mode, just like the G55 headers 😞.

In file included from modm/src/modm/platform.hpp:40,
                 from main.cpp:12:
modm/src/modm/platform/timer/timer_channel_0.hpp: In static member function 'static void modm::platform::TimerChannel0::setWaveformSelection(modm::platform::TimerChannelBase::WavSel)':
modm/src/modm/platform/timer/timer_channel_0.hpp:131:11: error: 'TC_CMR_WAVEFORM_WAVSEL_Msk' was not declared in this scope
  131 |   cmr &= ~TC_CMR_WAVEFORM_WAVSEL_Msk;
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~

[chris-durand]

CI is green now. Fixing the header issue was easy since the fix was already there for SAMG5 devices. Should be ready to merge.